Power supply circuit



Oct. 10, 1967 R. E. LYNN POWER SUPPLY C IRCUIT Filed Dec. 28, 1964 j AMPLIFIER CONTROL "figure 1 T WE 1i 19 SSQJZPEZ v Fi ure 2 INVENTOR ROBERT E. LYNN BY QC- ATTORNEY United States Patent 3,346,803 POWER SUPPLY CIRCUIT Robert E. Lynn, Somerville, N.J., assignor to Hewlett- Packard Company, Palo Alto, Calif., a corporation of California Filed Dec. 28, 1964, Ser. No. 421,400 1 Claim. (Cl. 323-22) ABSTRACT OF THE DISCLOSURE A quick-discharge circuit across the output terminals of a regulated power supply is controlled by the signal applied to the regulating element for shortening the time required to decrease the regulated output voltage to a lower final value.

It is an object of this invention to provide a regulated power supply circuit which includes a regulator driving element that serves as a current conductor in the discharge path of the output capacitor during down-adjustment of the output, and another object is to provide an improved rapidly programmable regulated power supply.

In accordance with embodiments of the invention which are illustrated in FIGURES 1 and 2 of the accompanying drawings showing circuit diagrams of the invention, a source 9 of unregulated unidirectional voltage is connected to supply voltage to the output terminals 11, 13 through serially-connected regulator 15 and resistor 17. Variations in the output voltage about a given value are sensed by control amplifier 19 which supplies a regulating base signal to driver transistor 21. The output at the emitter of transistor 21 supplies 'a regulating base signal to the regulator 15 to control its conductivity in proper sense to maintain the output voltage at the given value. Source 23 and resistor 25 supply bias current for the base of regulator 15 and for the emitter of driver 21. This source 23 and resistor 25 (aided by the voltage drop across resistor 17) also tends to back bias diode 27 of FIGURE 1 and to reverse bias the transistor 37 of FIG- URE 2 during normal operation. Capacitor 29 charges to the output voltage which is applied to load 31. If the output voltage is then suddenly reduced, as by changing the operating conditions of control amplifier 19 and drive-r 21 in a manner commonly known to render regulator 15 less conductive, capacitor 29 must be discharged. If the load resistance 31 is high, discharge may be undesirably slow.

Since the output of control amplifier 19 becomes more positive (for transistor types shown) during down-adjustment of the output voltage, the driver 21 becomes more conductive, thereby making the base of regulator 15 and the anode of diode 27 in FIGURE 1 (or the base of transistor 37 in FIGURE 2) more positive. This renders regulator 15 less conductive 'and forward biases diode 27 in FIGURE 1 (or the transistor 37 in FIGURE 2) to conduction, thus providing a highly conductive path through driver 21 and diode 27 in FIGURE 1 or a highly conductive path through transistor 37 in FIGURE 2 for discharge current from capacitor 29. This results in rapidly decreasable output voltage, independent of load resistance.

I claim:

A regulated power supply comprising:

a pair of output terminals;

a source of undirectional voltage having one terminal connected to an output terminal of the power supply and having another terminal;

a transistor regulator of one conductivity type having a base electrode and an emitter-collector current conduction path connected in circuit between the other terminal of said source and another of said pair of output terminals;

control means connected to said output terminals for producing a control signal related to the variations of the voltage across said output terminals about a selected value;

a transistor amplifier of the opposite conductivity type having a base electrode connected to receive the control signal from said control means and having a collector-emitter current conduction path;

means connecting the base electrode of said transistor regulator to the current conduction path of said transistor amplifier for receiving signal therefrom to control the conductivity of the regulator in proper sense to maintain the voltage across the output terminals at said selected value;

a diode; and

a discharge circuit including said diode and the collector-emitter current conduction path of said transistor amplifier serially connected in a common current conduction direction between said output terminals for providing a current conduction path in said common direction in response to control signal applied to said transistor amplifier to decrease the conductivity of said transistor regulator.

References Cited UNITED STATES PATENTS 3,076,135 1/1963 Farnsworth 323-22 3,124,698 3/1964 Semmer et al. 32322 3,284,692 11/1966 Gautherin 323-22 3,286,157 11/1966 Leostic 32322 JOHN F. COUCH, Primary Examiner. M. L. WACHTELL, Assistant Examiner. 

